The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
A gas-fired, warm air furnace that operates at two or more gas flow rates is generally referred to as a variable or multistage furnace. Multistage furnaces are frequently selected by homeowners for replacement of existing furnaces because they offer increased performance and comfort. However, in multi-stage or variable heating furnaces, the furnace control is only configured for one-way communication with a gas valve. This typically is in the form of a signal applying a voltage source or a variable current signal to the gas valve. However, such signals are not capable of providing feedback, and may not be compatible with replacement or retrofit of gas valves or other components of the furnace. Accordingly, a need still exists for an improved control of variable stage heating systems.